Sen. Claire McCaskill may be politically vulnerable and among the GOP’s top 2012 targets, but that hasn’t stopped Republicans from cooperating with the Missouri Democrat on legislation that could raise her standing back home.

At least two Democratic Senate aides who work for targeted and potentially vulnerable Members acknowledge that pushing bipartisan legislation is essential to their political strategy for winning re-election, saying that they actively seek opportunities to work with Republicans as a means to build credibility with their states’ significant population of conservative voters. Senate Republicans contend that such an effort is fruitless — at least in McCaskill’s case.

The GOP argues the first-term Senator is doomed in 2012 for, among other reasons, her support for President Barack Obama’s agenda, particularly his health care overhaul. With that in mind, Republicans said they see no reason not to collaborate with McCaskill on conservative priorities as they attempt to build the 60-vote coalition necessary for major Senate legislation. If this bipartisanship leads to Democratic infighting and pits Senate Democrats against Obama, all the better. In fact, Sen. Bob Corker said his Conference was supportive of his work with McCaskill on a spending reduction bill.

“I’ve had no pushback,” said the Tennessee Republican, who is also up for re-election. “Our caucus wants to see something happen that matters, that’s substantial, that’s in the trillions of dollars category, and I think everyone knows, in order to do that, you’ve got to have 60 votes, and we have 47.”

In addition to working with Corker, McCaskill recently penned a letter with freshman Sen. Rob Portman (R-Ohio) asking the Obama administration to abandon a plan that would require companies that contract with the government to disclose political activity. Previously, she has worked with Republican Sens. Tom Coburn (Okla.) and Jim DeMint (S.C.), both conservative stalwarts, on earmark reform, and with Sen. David Vitter (R-La.) on a bill to halt Congressional pay raises.

McCaskill declined to comment on whether her cooperation with Republicans would boost her political prospects.

“I’m trying not to do the political play-by-play on this stuff,” McCaskill said. “I’ve tried to work across the aisle because it makes it more likely that you’re going to pass something and get something done. To me, the only way we solve problems around here is by compromising and working together. Unfortunately, solving problems and winning elections — around this place — is too often like oil and water.”

One Democratic operative familiar with McCaskill said her penchant for bipartisanship serves the Missourian well as a legislator — and politically. And some Republicans cautioned that rhetorical praise for McCaskill as a fiscal conservative, as Corker has offered, could be helpful to the Democrat in her re-election bid. Senate aides said it was pointed out to Corker internally that this was not helpful.

Missouri is a perennial swing state, with elections often decided by independent voters. In 2006, McCaskill narrowly ousted Jim Talent (R), 49.6 percent to 47.3 percent. Obama lost Missouri to Sen. John McCain (R-Ariz.) in 2008, and the president’s health care law is so unpopular there that Democratic state Attorney General Chris Koster is on record opposing it.

A Democratic Senate aide whose boss is running for re-election in another state where Obama and his health care law are unpopular said accruing a bipartisan record on legislation is a political priority.

“I can’t overstate the importance of working across the aisle,” this aide said. “It’s where my boss is philosophically. People in our state want to see politicians come together and rebuild our country. They don’t care about party labels; they care about solutions. We have and will continue to seek out opportunities to work with our colleagues from both parties.”

Republican operatives, including those with Senate clients and those who have previously worked at the National Republican Senatorial Committee, were split as to whether GOP Senators are jeopardizing their party’s chances of beating McCaskill and retaking the Senate by cooperating with her on legislation. Some suggested that McCaskill is being granted cover by Republicans that will give her credibility with conservative voters in 2012.

But GOP operatives said that absent a game-changing piece of legislation that would amount to a complete rejection of the Obama agenda, voters pay little attention to the legislative activity on Capitol Hill and are more likely to punish McCaskill for her health care vote and her close association with the president. In fact, Republican Senators are thrilled with Portman for his collaboration with McCaskill on the government contracting issue.

In addition to their philosophical opposition to the proposed rules for contractors, Senate Republicans fear that forcing donor disclosures could hamper fundraising efforts by GOP-leaning political groups that have become integral to supporting Republican campaigns across the country. NRSC Chairman John Cornyn (Texas) acknowledged this fear while dismissing suggestions that McCaskill might salvage her political standing through bipartisanship on legislation.

“I think the public is smart enough to recognize election-year conversions. We all, frankly, have a longer record of voting on issues, like the health care bill,” Cornyn said. “I don’t have any concerns about Members trying to do what they can to pass legislation that will help the country. I just think we need to look at the big picture.”